本研究為了解紅類星體的性質，使用史隆數位巡天計畫第七次資料釋出的類星體目錄，及其測光資料與光譜。並選用靜止坐標系下1750Å、2200Å、3100Å與4000Å的平均通量密度計算色指數，得到三組不同的色指數。以此三組色指數定出紅類星體及典型類星體。 我們使用塵埃吸收模型，來探討紅類星體是否成因於塵埃的吸收。若是紅類星體的成因全部來自於塵埃的吸收，則AV = 0.2~0.8即可達到本研究所定義之紅類星體標準。另外我們也使用完整的光譜來檢驗紅類星體，是否能由塵埃吸收所造成。由兩組色指數所定出的特別紅的類星體中，在有1750Å、2200Å與3100Å特別紅的紅類星體中，有27/35個紅類星體可用塵埃的吸收解釋。在有2200Å、3100Å與4000Å的特別紅類星體中，133/154可用塵埃吸收解釋。 本研究從光度與色指數的關係中發現似乎存在一個明顯的藍色邊界，使得色指數偏藍且亮的類星體數量偏少，本研究稱為此現象「為消失的藍類星體」。推測原因可能與中心黑洞質量或吸積速率有關，但從粗略的檢查方式無法確定直接的關聯性。故目前對此現象產生的原因尚未明白。;To investigate the origin of red quasi-stellar objects (QSOs), we studied the color and physical properties of the QSOs selected from the Sloan Digital Sky Survey (SDSS) using both spectral and photometric information. We choose 1750 Å, 2200 Å, 3100 Å and 4000 Å mean flux density at rest frame to calculate the colors of QSOs. We defined ‘red QSOs’ and ‘typical QSOs’ with three different colors. If the ‘red QSOs’ were due to dust extinction, they need Av = 0.2~0.8 to reach the definitions of ‘red QSOs’ in this study. We also investigate the red QSOs with the whole spectra of SDSS. Some extreme red QSOs defined in two different colors can be explained with dust extinction. There were 27/35 red QSOs, which had red colors defined with 1750Å, 2200Å and 3100Å band fluxes, could be explained with dust extinction. There were 133/154 red QSOs, which had two colors defined with 2200Å, 3100Å and 4000Å band fluxes, could be explained with dust extinction. There is a clear boundary on the color-luminosity diagrams of the QSO. The blue and bright QSOs seem to be missed. We called this phenomenon ‘the missing blue QSOs’. It might be related to the central black hole mass of QSOs or accretion rates. However, we could not get a clear relation with a simple test of the data. The origin of the missing blue QSOs is still unclear.
